Why is my cycles render still grainy on 1000 cycles?
I see a few things you can improve:


You can use much less polygons. The higher the polygon count, the longer the render will take. Try searching for tutorials that use subdivision ("subdiv") modifiers.
Use a cube instead of a collection of planes. There are gaps between the planes, which makes it harder for Blender to analyze the scene. Using a gapless cube will improve the rendering.
Reduce the number of light bounces; this is what I used in the render below: 
Use GPU rendering if you have an NVidia or AMD video card:

Reduce the number of samples (because by now you don't need that many).  I used 100 samples instead of 1000 in the render below.


This is the result (except the polygon count, I kept the lamp model the same), which was rendered in just under a minute on an NVidia Geforce GTX 970.